Rearrangement and somatic mutation contribute to primary antibody repertoire diversification in cattle. Untemplated somatic mutation, gene conversion, or a combination of both, is thought to be the major generator of repertoire diversification in the Bovidae. However, much of the repertoire of heavy and light chain V genes in cattle and sheep remains unknown. Thus, it is difficult to determine, definitively, whether particular variations in expressed antibody genes are due to mutation or rearrangement. It is also difficult to discriminate between gene conversion and untemplated somatic point mutation. The proposed studies entail experiments that will use variation in J-C intron sequences to resolve these issues. The following specific aims were listed: 1) Use of the J-C intron as a diagnostic indicator of the mutational mechanisms used in bovine lambda light chain diversification. 2) Use of the bovine heavy chain J-C intron as a neutral indicator of bovine heavy chain mutational diversification. 3) Use of the J-C intron as a diagnostic indicator of the mutational mechanism employed in bovine heavy chain mutational diversification. Examination of the J-C intron provides both a neutral indicator of mutation and a way a to discriminate between gene conversion (templated mutation) and somatic mutation (untemplated mutation). Characterization of light and heavy chain J-C introns and demonstration of their utility as "mutometers" for detecting the occurrence and mechanism of mutation in bovine antibody genes will establish a useful tool for analysis of variation in bovine Ig genes. The applicant proposes that this approach may provide a convenient assay for future study of somatic mutation of bovine immunoglobulin genes in organ and cell culture.